1. Technical Field
The present invention relates to a forgery prevention medium and particularly to a forgery prevention medium that makes use of a hologram applied for determining authenticity to prevent forgery.
2. Background Art
Various means of preventing forgery have been used for goods that need forgery prevention as well as authentication, such as cards including cash cards, credit cards and check cards, cash vouchers, identification papers, and important documents. For example, a rainbow hologram consisting of a relief hologram having a metallic reflective layer is provided as a structure for authentication on the surface of the credit card to allow a visual determination of the card's authenticity. A recording device for such a hologram is disclosed in JP-B-60-30948.
There is a technique for recording information on such a hologram, managing data, and verification. After the recording of hologram, printing is done on the surface of the hologram to record information on the hologram. As shown in FIGS. 12A to 12C, recorded as information are barcodes (FIG. 12A), two-dimensional barcodes (FIG. 12B), serial numbers (FIG. 12C), and the like. Although visual inspection may not lead to an understanding of the recorded information, it can be confirmed that some sort of information has been recorded. Since it is possible to visually confirm the presence of the information, the hologram can be forged by printing the same information even if the content of the information cannot be understood.
Therefore, a method of recording information with UV or IR emission ink would be used to make it impossible to visually confirm the recorded information.
Incidentally, techniques for printing information on holograms are disclosed in JP-A-62-133476, JP-A-2004-268258, and Jpn. PCT National Publication No. 2005-006166.
However, according to the conventional methods, when individual information is recorded, the recorded information could disturb and hurt the design of the hologram. A specific area on which the individual information is printed needs to be provided to keep the individual information from disturbing the design. However, the problem is that providing the specific area leads to an increase in the size of the hologram. The method of recording information with UV or IR emission ink can prevent the recorded information from disturbing the design of the hologram. However, there is a problem of increasing costs due to the necessity of selecting recording methods or materials to make it impossible to visually confirm the recorded information. Moreover, productivity is not good because the information needs to be positioned appropriately relative to the design.